
Certified GKH Gardening Expert
Unless you live in an area with mild winters, you need to dig up your dahlias. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/bulbs/bgen/storing-bulbs-in-south.htm
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/preparing-bulbs-for-winter-how-to-store-bulbs-for-winter.htm
This article will help you with your begonias: https://www.gardeningknowhow.com/ornamental/flowers/begonia/wintering-begonias-overwintering-a-begonia-in-cold-climates.htm